Switching apparatus



Dec. 13, 1955 J. E. SUNDERLIN 2,727,159

I SWITCHING APPARATUS Filed June 14, 1954 2 Sheets-Sheet l Fig.l. 20

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SWITCHING APPARATUS Filed June 14, 1954 2 Sheets-Sheet 2 Fig. 6.

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90 IIIIHIHIHIF W IAImmmIm United States Patent SWITCHING APPARATUSApplication June 14, 1954, Serial No. 436,419 7 Claims. (Cl. 307-106)This invention relates to switching apparatus, and more particularly tomagnetic switching apparatus for supplying recurring pulses to a loadthat appears resistive during the time of the output, such as amagnetron.

The pulses that are utilized for pulsing a magnetron are generally highpower recurrent pulses of very short duration compared to the intervalbetween pulses. A prior art device for producing recurrent pulsesoperates on the principle of the periodic storage of energy in aninductive system, the transfer of that energy to a storage capacitor andfinally the discharge of that energy to the load circuit. The buildingup of energy 'in th e inductive system is initiated by the periodicconduction of a control tube whose conduction is regulated by apulsating voltage supplied to the grid of the control tube.

It is an object of my invention to provide an improved switchingapparatus for supplyingrecurring pulses to a load.

It is another object of my invention to provide a magnetic switchingapparatus in which no, electron discharge devices are employed and hencethe apparatus is quite m s a It is an additional object to provide amagneticjswitching apparatus in which saturablereactors, having cores ofa material which exhibits a rectangular'hysteresisloop, are employed ina relatively simple circuit for pulse forming. I

' It is still another object to provide a magnetic switching apparatusin which the rate of pulses supplied to a load by the apparatus is twicethe frequency of the input to the apparatus, without the use of rotatingequipment to produce the frequency doubling. 7 i

It is a still further object of my invention to'provide a magneticswitching apparatus in which the rate of pulses supplied to a load bythe apparatus is triple" the frequency of the three-phase input signalto the apparatus.

These and other objects of the invention are effected as will beapparent from the following description, taken inaccordance with theaccompanying drawings, which form a part of this application and'in'which like numerals are employed to designate like parts throughout thesame:

Figure 1 is a schematic diagram of a magnetic switching apparatus inaccordance with a first; embodiment of my invention;

Fig. 2 graphically illustrates the output .voltage wave of theembodiment of my invention shown in Fig. 1;

Fig. 3 is a schematic diagram of a magnetic switching apparatus inaccordancewith a second embodiment of my invention in which a multiplexpulse shaping network isemployed;

Fig. 4 graphically illustratesthe output voltage wave of the embodimentof .my invention shown in Fig. 3;

Fig. 5 is a schematic diagram ofla magnetic switching apparatus inaccordance with a third embodiment of my invention, in which asaturating centertap transformeris utilized; r

Fig. 6 graphically illustrates the output voltage wave of the embodimentof my invention shown in Fig. 5;

Fig. 7 is a schematic diagram of an equivalent circuit of the circuitillustrated in Figure 5, with a conventional centertap transformer beingutilized in the equivalent circuit;

Fig. 8 is a schematic diagram of a magnetic switching apparatus inaccordance with a fourth embodiment of my invention with the apparatusbeing adaptable for operation from a three-phase power supply to effecta pulse tripping of the frequency of the input power.

In Fig. 1, there is shown a schematic diagram of a circuit of a magneticswitching apparatus in accordance with one embodiment of the presentinvention in which an inductor 16 is serially connected with capacitor18 and this series combinationforms a charging circuit which is placedin parallel with an alternating signal source 10, with source 10 beingconnected to the circuit through the connecting means 11 and 12. Thisconnecting means may be of any known prior art type. Inductor 16 has afixed inductance and is utilized to isolate capacitor 18 from the source10 when the capacitor is discharged. The various combinations ofdiiferent values of inductance and capacitance will determine the shapeof the charging voltage on the capacitor 18, i. e., the input chargingcircuit may be resonant or non-resonant. A saturating reactor 20 isconnected in a series arrangement with load 15 and this seriesarrangement is shunted by capacitor 18. Load 15 is connected with theoutput of the magnetic switching circuit through connecting means 13 and14. Saturating reactor 20 is preferably wound on a core of a materialwhich exhibits a rectangular hysteresis loop, more commonly known as asquare loop material. Materials of this type when used in the form ofcores for reactors or transformers exhibit a very large change inimpedance, e. g., 1000 to 1, when driven from the unsaturated conditioninto saturation. The circuit may be grounded at junction 17. I

The combined impedance of the reactor 20 when it. is unsaturated andload 15 should be much greater than the impedance of capacitor 18. Thisis necessary in order that there is very little shunting of thecapacitor 18 during the charging cycle. The impedance of the reactor 20when it is unsaturated should be much greater than the impedance of theload 15. This effectively causes all of the charging voltage oncapacitor 18 to appear across the reactor 20. The. type of reactor 20should be so chosen that when it becomes saturated its impedance shoulddrop to a value that is much less than the impedance of the load 15. Thecombination of the impedances of the load 15, the capacitor 18, and thereactor 20 when saturated, should be such that the discharge ofcapacitor 18 takes place in a short time compared with the time of theinput cycle. This allows the charging circuit to operate in a stablemanner- In Fig. 3 there is shown a schematic diagram of a circuit of amagnetic switching apparatus in accordance with a second embodiment ofthe present invention by which pulses of one polarity are. produced.Inductor 36 is serially connected with capacitor 38 and this seriescombination forms a charging circuit which is placed in parallel with analternating signal source 30, which source to the respective reactoracross 30 being connected to the circuit through the connecting means 32and 33. A saturating reactor 40 is connected in series arrangement withcapacitor 41 and this series arrangement is shunted by capacitor 38.Reactor 40 is provided with an auxiliary winding'47 which may beconnected to a source of direct voltage through impedance 111. Impedance111, aswell as all the impedances 112 116 used in the bias windings inthecircuits in accordance with my invention, has a high A. CL impedancerelative which it 'is connected.

A pulse shaping network having input connectors 101 and 102 and outputconnectors 103 and 104 is provided in this circuit with the networkconsisting of a plurality of serially connected saturating reactors,such as reactors 42, 44 and 46, with the saturating reactors beingshunted by a plurality of parallel capacitors, such as 41, 43 and 45.One or more of the reactors 42, 44 and 46 may require a means forsupplying a D. C. bias potential to the reactor such as winding 106 withimpedance 110 on the reactor 42. A pulse transformer 48. seriallyconnected with the last reactor 46, is provided to inductively couplethe output of the pulse shaping network with the connectors 34 and 35for connecting a load to the circuit. The circuit may be grounded atjunction 39. In selecting the inductor 36, capacitor 38 and saturatingreactor 40, relative values of the latter elements of the circuit shouldbe similar to the ones suggested for the inductor 16, capacitor 18 andsaturating reactor 20 in the circuit shown in Fig. l. Saturatingreactors 40, 42, 44 and 46 should have cores made of a thin square loopcore material to minimize eddy current effects. It should be understoodthat the number of serially connected reactors and parallel shuntcapacitors utilized in the circuit is determined by the amount of pulsenarrowing that is desired to be produced by the circuit.

In Fig. 5, there is shown a schematic diagram of a circuit of a magneticswitching apparatus in accordance with a third embodiment of the presentinvention in which a saturating transformer 63 is utilized with thetransformer having a primary winding, which is divided into two portions65 and 66 by centertap 64, and a secondary winding 67. A bias winding 62including the impedance 49 may be provided for supplying a D. C.potential to saturating transformer 63 for biasing the transformer. Aninductor 55 is serially connected with capacitor 56 to form a chargingcircuit and this charging circuit is connected in parallel with analternating signal source 50 by means of connectors 51 and 52. Two loopdischarge paths are provided for capacitor 56. One path includes asaturating reactor 60, provided with an auxiliary winding 61, includingthe impedance 113, which winding may be connected to a source of directcurrent with the reactor 60 being connected in series with the firstportion 65 of the primary winding of the transformer 63. The second pathfor the discharge of the capacitor 56 includes a saturating reactor 58,provided with an auxiliary winding 59, including the impedance 112,which winding may be connected to a source of direct current, with thereactor 58 being connected in series with the second portion 66 of theprimary winding of the transformer 63. Reactors 58 and 60 should be sobiased by the flux from windings 59 and 61, respectively, that reactor58 will become saturated only during one half of the cycle of the inputsignal to the circuit and reactor 60 will become saturated only duringthe other half of the cycle of the input signal to the circuit. Thesecondary winding 67 of the transformer 63 is connected with capacitor68 and load 57 in a series arrangement, with load 57 being connected tothe capacitor 68 and Winding 67 by means of connectors 53 and 54.Reactors 58 and 60 and saturating centertap transformer 63 shouldcontain cores of magnetic material having a rectangular hysteresis loop.

In Figure 7 is shown a circuit that is similar to the circuit shown inFigure 5. However, in the circuit shown in Figure 7, a conventionalcentertap transformer 63 is used instead of a saturating centertaptransformer. The secondary winding 67 of the transformer 63' is shuntedby capacitor 68' and is connected in a series arrangement withsaturating reactor 69 and load 57, with load 57 being connected to thereactor 69 and winding 67 by means of connectors 53 and 54.

In Figure 8 is shown a schematic diagram of a magnetic switchingapparatus in accordance with a fourth embodiment of my invention whichis operable with a three-phase power supply. Three separate chargingcircuits are provided. Each charging circuit consists of an inductor andcapacitor in series arrangement with one end of the capacitor grounded.In the embodiment shown, the three charging circuits comprise inductor76 and capacitor 80, inductor 77 and capacitor 81, and inductor 78 andcapacitor 82, respectively. Each of the three charging circuits isconnected to a three-phase power supply 70 by means of connectors 71, 72and 73. Saturable reactors 85, 86 and 87 are provided with respectivemain windings 91, 92 and 93 on each of which windings are two endconnector members. The respective auxiliary windings 95, 96 and 97,including the respective impedances 114, 115 and 116, are adaptable forconnection to a direct-current source for biasing. One end connectormember of each of the reactors is connected to the respective chargingcircuits at the junctions where the respective capacitors and inductorsare connected in such a manner that the capacitors 80, 81 and 82 mayfacilitate the saturating of reactors 85, 86 and 87, respectively. Theother end connector member of the main windings of the reactors areconnected together in a common junction 88. Reactor and connector 74 areconnected in a series arrangement with this junction 88. Connector 74 isprovided as means for applying a load 75 to the circuit. Load 75 shouldbe grounded as shown in the diagram. Also connected to common junction88 and being in parallel arrangement with the above series arrangementis capacitive member 89. Member 89 is also grounded as shown in theschematic diagram.

In accordance with the first embodiment of my invention shown in Fig. 1,an alternating signal from signal source 10 is supplied to the circuitthrough connectors 11 and 12. Initially there is no voltage on capacitor18 and reactor 20 is unsaturated. As the voltage of the capacitor rises,a change of flux occurs in the core of the reactor 20. The reactor isdesigned so that when the voltage on the capacitor 18 has reached itspeak, the core of the reactor will become saturated. The saturation ofthe core of reactor 20 causes a very great drop in the impedance of thereactor. Consequently, the capacitor 18 is now shunted by a lowimpedance path and discharges its energy into the load 15. The shape ofthe output voltage wave to the load is illustrated in Fig. 2.

In accordance with the second embodiment of my invention shown in Fig.3, an alternating signal from signal source 30 is supplied to thecircuit through connectors 32 and 33. Similar to the operation of thecircuit illustrated in Fig. l, the voltage across capacitor 38 tends tosaturate the core of reactor 40. However, the core of the reactor 40 isso biased that it will become saturated during only one half of thecycle of the input signal. Hence pulses of one polarity will beproduced. A resonant circuit is formed when reactor 40 saturates. Theresonant circuit consists of capacitors 38 and 41 and the reactor 40which has become saturated. The voltage on capacitor 41 will appear as apulse considerably reduced in width when compared with the voltage waveform on capacitor 38. The wave form then passes through the rest of thepulse shaping network including serially connected reactors 42, 44, 46and parallel capacitors 43 and 45, and is inductively coupled by meansof a pulse transformer to the connectors 34 and 35 to which a load maybe applied. 'lghe iutput voltage wave of the circuit is illustrated inIn accordance with the third embodiment of my invention shown in Fig. 5,an alternating signal from signal source 50 is supplied to the circuitthrough connectors 51 and 52. A suitable D. C. bias potential may besupplied to the winding 62 of the saturating transformer 63. Inductor 55and capacitor 56 are provided as an alternatingcurrent resonant chargingcircuit with the capacitor 56 being discharged every half cycle of theinput signal. This results in positive and negative pulses. Reactors 58and 60 are so biased by direct current being supplied to their auxiliarywindings 59 and 61, respectively, that onereactor saturates when thevoltage on capacitor 56 reaches its positive peak and the other reactorsaturates on the reverse peak polarity. By feeding these pulses into thesatu rating centertap transformer 63 through winding 65 when reactor 60is saturated and then through winding 66 during the other half of thecycle of the input signal when reactor 58 is saturated, the flux in thecore of transformer 63 is caused to fluctuate in magnitude in onedirection only and hence output pulses of one polarity will result andthese pulses will occur at a rate which is twice the fre quency of theinput signal to the circuit.

It should be pointed out at this time why a saturating centertaptransformer 63 is utilized in this circuit rather than a conventionalcentertap transformer. When capacitor 56 is discharged, it forms aresonant circuit with capacitor 68 and the saturated inductance ofreactor 58 or reactor 60, depending on which reactor is in the saturatedstate. The values of these circuit components, capacitors 56 and 68 andreactors 58 or 60, are so chosen in order that some pulse sharpeningoccurs. During the time capacitor 56 is discharging into capacitor 68,the transformer 63 operates as a conventional transformer. Thetransformer 63 should be so chosen that it will become saturated whenthe voltage on capacitor 68 reaches its maximum value. A new resonantcircuit is now formed which comprises capacitor 68, the transformer 63which has become saturated and the load 57. Consequently, more pulsesharpening occurs and in the circuit shown in Fig. the narrowed pulsesare dissipated into the load 57. However, the pulses could be passedthrough an additional pulse sharpening network before supplying them toa load. In Fig. 6 is illustrated the output voltage wave supplied to theload 57 in the circuit shown in Fig. 5.

By referring to Fig. 7, it can be seen that an additional component,saturating reactor 69, must be added to the circuit in accordance withthe third embodiment of my invention when a conventional centertaptransformer 63 is used instead of a saturating centertap transformer, ifit is desired to obtain the same amount of pulse sharpening as wasobtained from the circuit illustrated in Fig. 5. In other words, Fig. 7is an equivalent circuit of Fig 5 when a conventional centertaptransformer 63' is used instead of the saturating centertap transformer63. The circuit shown in Fig. 7 operates in the same manner as thecircuit shown in Fig. 5 up until the time when capacitor 68 is receivingthe charging voltage. The saturable reactor 69 should be so chosen thatit will become saturated when the voltage on capacitor 68' reaches itsmaximum value. A new resonant circuit is formed which comprisescapacitor 68, the reactor 69 which has become saturated and the load 57.Consequently, pulse sharpening occurs as is the case in the circuitillustrated in Fig. 5.

It can be seen from the above description that by utilizing a saturatingcentertap transformer in this particular embodiment of my invention,additional pulse sharpening can be obtained which could otherwise bebrought about only by use of an additional component, namely, asaturable reactor. The elimination of the necessity of utilizing theadditional saturable reactor for obtaining the desired pulse sharpeningwill result in a savings in space and weight which is quite a factorwhen the circuit in accordance with this embodiment of my invention isutilized in equipment for the military.

In accordance with the fourth embodiment of my invention as shown inFig. 5, a three-phase alternating signal comprising phases A, B and C issupplied to the circuit through connectors 71, 72 and 73. Let us firstconsider phase A. With a proper bias on winding 95 of reactor 91 so thatthe reactor can become saturated during only one-half of a cycle ofphase A, capacitor 80 will charge up to some peak value. At this pointreactor 91 becomes saturated and capacitor 80 discharges into capacitivemember 89. When the charge on capacitive member 89 reaches its peakvalue, reactor 90 becomes saturated and member 89 discharges into theload 75. Each time a discharge takes place, some pulse sharpeningoccurs. Phase B and phase C cause similar charging and discharging ofcapacitors and 81 respectively, with the aid of reactors 86 and 87 in amanner as described above for phase A. Capacitive member 89 receivespulses at a rate which is three times the input frequency and suppliesthem to load 75. is within the scope of this embodiment of the inventionto remove capacitive member 89 and reactor 90 from the circuit andconnect the load 75 through connector 74 directly to junction 88.However, the pulses would lack the desirable pulse sharpening which iseffected by the charging and discharging of capacitive member 89.

While I have shown the use of my invention in several embodiments, itwill be obvious to those skilled in the art that it is not so limitedbut is susceptible to various changes and modifications withoutdeparting from the spirit thereof. For example, in all of the suggestedembodiments of my invention, additional pulse sharpening components,including additional capacitors and reactors with cores of a materialhaving a rectangular hysteresis loop, could be added to the circuits ofthe disclosed embodiments without departing from the scope of myinvention. Further, the load may be of any type which appears resistiveduring the time of output.

I claim as my invention:

1. A magnetic switching circuit for applying recurring pulses to a load,said circuit comprising first means for applying a signal to saidcircuit, second means for connecting a load to said circuit, aninductor, a capacitor and a saturable reactor, said saturable reactorbeing serially connected with said second means, said inductor and saidcapacitor being connected in a series circuit, with said series circuitbeing connected in parallel arrangement with said first means, saidserially connected saturable reactor and second means being shunted bysaid capacitor in such an arrangement that the voltage across thecapacitor saturates the saturable reactor, said saturable reactor afterbeing saturated thereby forming a low impedance path for the dischargeof the capacitor into said load.

2. A switching circuit for applying recurring pulses to a load, saidcircuit comprising first means for applying a signal to said circuit, aninductor and a capacitor serially connected, said serially connectedinductor and capacitor being connected in a parallel arrangement withsaid first means, a saturable reactor provided with a biasing winding, apulse shaping network, said saturable reactor being serially connectedwith said pulse shaping network, said serially connected saturablereactor and pulse shaping network being connected in a parallelarrangement with said first capacitor, and second means for connecting aload to said circuit, said second means being inductively coupled tosaid pulse shaping network.

3. A switching circuit for applying recurring pulses to a load andadapted to be connected between a signal supply and a load, said circuitcomprising an inductor and a first capacitor, said inductor being in aseries circuit arrangement with said first capacitor, said seriescircuit arrangement being adapted for connection in parallel with saidsignal supply, a saturable reactor member provided With a biasingwinding, a pulse shaping network including a plurality of branches, witheach of said branches including a serially connected saturating reactorand capacitor member, said saturable reactor member being provided in aseries circuit arrangement with the capacitor member of one of saidbranches, said latter series circuit arrangement being shunted by saidfirst capacitor, and an inductive coupling member, said inductivecoupling member providing a coupling between the saturating reactor ofone of said branches and said load.

4. A magnetic switching circuit for applying recurring pulses to a loadat twice the frequency of the alternating input signal to the circuit,said switching circuit Hence pulse tripling is achieved. It

including a serially connected inductor and capacitor, and first meansfor connecting said input signal to said circuit, with said seriallyconnected inductor and capacitor being connected in parallel with saidfirst means, a first and a second loop conductive path, with each ofsaid paths being shunted by said capacitor, first and second saturablereactors respectively provided with biasing windings, a saturabletransformer having a primary winding and a secondary winding, saidprimary winding having a center tap and a first portion and a secondportion, said first loop conductive path including said first saturablereactor serially connected with said first portion of the primarywinding of said saturating transformer, said first saturable reactorbeing biased such that it will become saturated during only one half ofeach cycle of the alternating input signal, said second loop conductivepath including said second saturable reactor serially connected with thesecond portion of said primary winding, said second saturable reactorbeing biased such that it will become saturated during the other half ofeach cycle of the alternating input signal, a second capacitor, andsecond means for connecting a load to said circuit, said secondcapacitor being connected in a series circuit arrangement with saidsecondary winding of said saturating transformer, with said seriescircuit arrangement being connected in a parallel circuit arrangementwith said second means.

5. A magnetic switching circuit for applying recurring pulses of onepolarity to a load at a rate which is twice that of the frequency of thealternating input signal to be supplied to the circuit, said switchingcircuit including a saturating transformer having a center tap, saidtransformer having a primary winding including first and second portionsand a secondary winding, a first conductive loop and a second conductiveloop, said loops being connected in a parallel circuit, each of saidloops being shunted by first means for supplying an alternating chargingvoltage to said loops, said first loop consisting of a first saturablereactor and said first portion of the primary winding, said firstsaturable reactor having second means for biasing said first reactor,said second loop consisting of a second saturable reactor and saidsecond portion of the primary winding, said second saturable reactorhaving third means for biasing said second reactor with said first andsecond saturable reactors being so biased that they will alternatelybecome saturated by said alternating charging voltage, said chargingvoltage thereby effecting the passage of a peaked fluctuatingunidirectional flux in the core of said saturating transformer, fourthmeans for connecting a load to said circuit, a capacitor, said fourthmeans and said capacitor and said secondary winding being seriallyconnected, with said capacitor being operative to saturate saidsaturating transformer to thereby sharpen the pulses supplied to saidload.

6. A magnetic switching circuit for applying pulses to a load at a ratewhich is three times that of the frequency of a three phase alternatinginput signal to be supplied to the circuit, said switching circuitincluding means for applying a three-phase supply signal to saidcircuit, first, second, third and fourth charging circuits, first,second, third and fourth saturable reactors, with said first chargingcircuit being connected in a first series circuit arrangement with saidmeans and said first saturable reactor, said second charging circuitbeing connected in a second series circuit arrangement with said meansand said second saturable reactor, said third charging circuit beingconnected in a third series circuit arrangement with said means and saidthird saturable reactor, said first, second and third series circuitarrangements being connected at a common point, said fourth chargingcircuit being connected to said common point, and said fourth chargingcircuit being connected in a fourth series circuit arrangement with saidfourth saturable reactor and said load.

7. A magnetic switching circuit for applying pulses to a load at a ratewhich is three times that of the frequency of the alternating inputsignal to be supplied to the switching circuit, said switching circuitincluding first, second, and third connectors adaptable for receivingsaid input signal, first, second and third pulse forming circuits, eachof said pulse forming circuits including an inductor member and asaturable reactor connected in series circuit arrangement to provide apoint of connection therebetween, a grounded capacitive member connectedto said point of connection, said respective first, second and thirdpulse forming circuits being serially connected with respectively thefirst, second, and third connectors, a fourth pulse forming circuitcomprising a series circuit arrangement of a capacitive member and asaturable reactor member, connector members adapted for connecting saidload to the switching circuit, said first, second and third pulseforming circuits being respectively connected to said fourth pulseforming circuit at a common point in such an arrangement that the pulsesproduced by the first, second, and third pulse forming circuits producea charging voltage on the capacitive member of said fourth pulse formingcircuit, said charging voltage thereby effecting the saturation of thesaturable reactor of said fourth pulse forming circuit.

References Cited in the file of this patent UNITED STATES PATENTS

